The present invention relates to a driving assembly for controllably driving a slide. The provision on base frameworks or beds of high precision parallel guides is already known.
Said parallel guides, in particular, are used for supporting thereon slides or uprights in turn supporting, for example, machining devices such as drilling devices, boring or milling assemblies as those conventionally used in the tool machine field.
In large machining shops, the movable slide frequently comprises a portal construction including machining and chip removing assemblies.
The portal construction forming the movable slide can be driven with respect to the workpiece, which is arranged on the machine bed.
For driving a slide of the above-mentioned type, are conventionally used driving motors which are operatively coupled to mechanical motor-reducing units or transmission means.
At the end portion of their kinematic chain, the prior devices comprise a pinion engaging with a rack rigid with the machine bed, thereby, as the pinion or pinions are rotatively driven, the slide is in turn controllably driven.
However, the use of conventional motors and mechanical motor-reducing units for driving a comparatively heavy slide or a portal construction on a bed, does not meet present precision requirements and, because of an elastic nature of the transmission means, does not result in an accurate repeatability of the machining slide displacements.
Accordingly, the aim of the present invention is to provide a novel driving assembly, designed for overcoming the above mentioned drawbacks affecting the prior art, which allows to controllably drive a slide or a portal construction with respect to a bed, with a very great precision and an accurate repeatability of the slide operating displacements.
According to the invention, the above aim is achieved by a driving assembly for controllably driving a slide with respect to a base including a rack that engages at least a pinion driven by a controllable motor having a motor shaft, a motor rotor and a motor stator, said motor rotor having a rotor shaft. The pinion forms a single body with said shaft of said motor. The shaft of said motor is rigid with a support element delimiting a circumferential chamber, to provide a body of said support element with a U-shape cross-section. The end portions of said rotor shaft of said rotor are supported by bearings engaged in recesses formed in cover elements rigidly coupled to a body of said motor stator.
By a driving assembly as above disclosed, it is possible to provide a monolithic and rigid body, formed by a pinion forming a single body with and integrated in the shaft of the rotor, by said rotor, and this owing to the provision of an intermediate supporting element defining an annular empty chamber, providing a weight reduction and an optimum cooling down of the overall assembly.
By engaging the end portions of the shaft of the rotor in recesses defined in strong cover elements rigid with the body forming the stator of the motor, a greatly rigid and compact body to be coupled to the slide to be driven is thereby obtained.
The electric motor is of a xe2x80x9cbrushlessxe2x80x9d type. The stator of said motor comprises a pack of stator laminations, combined with the stator coils and including a high number of poles; the rotor of said motor comprising a steel ring element including a plurality of permanent magnet plates, the assembly providing a loose ring stator and rotor brushless type of motor.